In the discovery/final reveal scenes the character Mrs Carlton is missing her right earring.
They conduct a DNA test on the assumption that the murder/suicide victim was Colin's father. It comes back that he was not. But it is later revealed that he was Colin's mother's first cousin. Surely the DNA profile would have revealed such a close family link.
When the team discover the victim could have been murdered rather than taking his own life, they find the pathologist found that postmortem lividity (blood settling after death) showed the victim's body had been moved after he died. As the victim was found moments after his death, postmortem lividity would not have begun.